Bruce McLachlan, chief executive of Fisher Funds, said his firm's modelling showed the optimal strategy for a mid-50s investor was to have 60% growth assets at 55 and more than 40% at 60. Even at 90, they would have 20% in growth investments.

"Our analysis suggests a much slower reduction in growth assets is the preferred KiwiSaver strategy," he said. "Because New Zealand started KiwiSaver so recently many fund managers are using lifestage models from overseas data, where retirement savings have been in place for much longer and at higher levels.

"Because most New Zealanders are way behind there is a need, indeed a requirement, for many to have more exposure to growth for longer."

By contrast, ANZ's Lifetimes KiwiSaver options guides investors over 60 into a conservative fund, and into cash over 65.

McLachlan said those who suggested risk be dialled down quickly were subscribing to a school of thought that arose in a time when life expectancies were less.

"We used to retire at 65 and die at 75. That led to a certain strategy. Now, life expectancy is 84 and on its way to 92. We all have to plan for life stages and that last life stage could be an extra 10 or 20 years. The strategy should be different."

But he said, rather than schemes making changes, New Zealanders' attitude needed alteration.

The amount of money people had lost over the last 10 years because of their conservative approach was massive, he said.

"It's everyone's job. It's clearly our job, the regulators, the media, the product providers - we all have an obligation to educate and share that knowledge."

McLachlan said too-conservative investment was a bigger concern than fees, which get more attention.

"If you're focused on, say 50 basis points of fees and you are missing out on 5% in investment returns, are you focusing on the right thing?"

He said the default KiwiSaver funds should be balanced, not conservative.

ANZ general manager of wealth products Ana-Marie Lockyer said people should be encouraged to check how their money was invested.

“As KiwiSaver becomes a larger part of New Zealanders’ retirement savings we agree  that members will need to consider how long they will continue to work and to save beyond the age of 65. They will also need to consider how long they wish to continue to stay invested in KiwiSaver and other retirement funds , and what their risk tolerance is at this stage of their life.  This will in turn drive what the right fund choice is for them .

While our lifetimes model gradually adjusts the risk return profile, we do encourage our members to seek advice at around  age 55 and also to consider at 65 how they would like to invest based on their financial position and working situation.   We will also continue to review in light of the decisions our KiwiSaver members are making.”